Processing state information

ABSTRACT

A method of operating a user equipment in a communications system including at least one cell that is controlled by a radio access node. The method includes maintaining current state information relating to the user equipment, the state information including at least one state information part associated with features for which state information reporting is configured in at least one cell, at least one state information part being associable with a plurality of different values, receiving an indication from the radio access node regarding state information held by the radio access node relating to the user equipment, determining whether to report current state information relating to the radio access node on the basis of the received indication, and reporting a current value associated with at least a given state information part to the radio access node.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 15/421,867, filed on Feb. 1, 2017, which is a continuationapplication of prior application Ser. No. 14/240,640, filed on May 1,2014, which is a U.S. National Stage application under 35 U.S.C. § 371of an International application filed on Aug. 22, 2012 and assignedapplication number PCT/KR2012/006651, which was based on and claimedpriority of a United Kingdom patent application filed on Aug. 22, 2011in the United Kingdom Intellectual Property Office and assigned Serialnumber 1114476.3, the disclosure of which is incorporated by referenceherein in its entirety.

TECHNICAL FIELD

The present invention relates to processing state information.

BACKGROUND ART

Up to, and including, Release 10 (REL-10) of the Long Term Evolution(LTE) 3rd Generation Partnership Project (3GPP) specification number TS36.300 “Evolved Universal Terrestrial Radio Access (E-UTRA) and EvolvedUniversal Terrestrial Radio Access Network (E-UTRAN); OverallDescription; Stage 2”, User Equipment (UE) reporting related to featuressuch as Radio Link Failure (RLF) information availability, loggedmeasurement information availability and proximity indication. It isexpected that additional reporting will be introduced, for exampleregarding Multimedia Broadcast Multicast Services (MBMS) interest andin-device interference, in later releases.

The UE repeats reporting of such information following every cell changein connected mode, in other words following every handover or connectionre-establishment. Some such information, such as RLF information andlogged measurement information, is contained in mobility-relatedmessages. Other information is (expected to be) transferred by means ofa separate, dedicated message. It is expected that the UE will need toprovide the E-UTRAN with more and more up-to-date information. It isexpected that reporting on the part of the UE will increase,particularly following a change in cell.

DISCLOSURE OF INVENTION Technical Problem

It would be desirable to provide improvements in processing informationrelating to user equipment.

Solution to Problem

According to a first aspect of the invention, there is provided a methodof operating a user equipment in a communications system comprising atleast one cell that is controlled by a radio access node, the methodcomprising:

maintaining current state information relating to the user equipment,the state information comprising at least one state information partassociated with one or more features for which state informationreporting may be configured in the at least one cell, the at least onestate information part being associable with a plurality of differentvalues;

receiving an indication from the radio access node regarding stateinformation held by the radio access node relating to the userequipment;

determining whether to report current state information relating to theuser equipment to the radio access node on the basis of the receivedindication; and

reporting a current value associated with at least a given stateinformation part to the radio access node in response to determiningthat current state information relating to the user equipment should betransmitted on the basis of the received indication.

As such, unnecessary reporting of state information may be reduced. Ifthe determination based on the received indication is that no reportingis required, or if no indication is received, the user equipmentpreferably refrains from transmitting a current value associated with agiven state information part to the radio access node.

In some embodiments, the determining includes determining that thecurrent value has not yet been received by the radio access node.

In some embodiments, the received indication comprises a versionidentifier indicating a version of the given state information part heldby the radio access node.

Some embodiments comprise including the determining includes determiningthat the version identifier does not correspond with a current versionof the given state information part.

Some embodiments comprise including a version identifier indicating thecurrent version of the given state information part when reporting thevalue associated with the given state information part to the radioaccess node.

Some embodiments comprise advancing the version identifier indicatingthe current version of the given state information part upon reportingthe value associated with the given state information part to the radioaccess node.

In some embodiments, the version identifier indicating a version of thegiven state information part held by the radio access node is a commonversion identifier that indicates a version of both the given stateinformation part and at least one additional state information part.

Some embodiments comprise reporting the value associated with the givenstate information part and a value associated with the at least oneadditional state information part to the radio access node.

Some embodiments comprise including a common version identifier whenreporting the value associated with the given state information part andthe value associated with the at least one additional state informationpart to the radio access node.

In some embodiments, the indication is received from the radio accessnode on the basis of a change of connection of the user equipment from afirst cell in the communications system to a second cell in thecommunications system.

According to a second aspect of the invention, there is provided userequipment for use in a communications system comprising at least onecell that is controlled by a radio access node, the user equipmentcomprising:

a data store for maintaining current state information relating to theuser equipment, the state information comprising at least one stateinformation part associated with one or more features for which stateinformation reporting may be configured in the at least one cell, the atleast one state information part being associable with a plurality ofdifferent values;

a radio interface for receiving an indication from the radio access noderegarding state information held by the radio access node relating tothe user equipment, and for reporting state information to the radioaccess node; and

a processor configured to determine whether to report current stateinformation relating to the user equipment to the radio access node onthe basis of the received indication, and for reporting a current valueassociated with at least a given state information part to the radioaccess node in response to determining that current state informationrelating to the user equipment should be transmitted on the basis of thereceived indication.

According to a third aspect of the invention, there is provided a methodof operating a user equipment in a radio access network comprising cellsthat are controlled by radio access nodes, the method comprising:

maintaining current state information relating to the user equipment,the state information comprising at least one state information partassociated with one or more features for which state informationreporting may be configured in a cell, the at least one stateinformation part being associable with a plurality of different values;

initiating first reporting of a current value associated with at least agiven state information part to a radio access node;

activating a timer on the basis of the initiation of the firstreporting;

determining whether to initiate second reporting of the current value toa radio access node on the basis of one or more predetermined triggers;and

initiating second reporting of the current value in response todetection of one of said of one or more predetermined triggers beforeexpiry of a timing period measured by said timer.

As such, unnecessary reporting of state information may be reduced. Ifthe timing period measured by said timer expires without detection ofone of said of one or more predetermined triggers, the user equipmentpreferably refrains from transmitting a current value associated with agiven state information part to the radio access node, and a radioaccess node may obtain the value by other means, such as by transfer ofthe information from another radio access node. The current valueassociated with a given state information part then does not need to betransmitted over the air interface if the user equipment refrains fromsuch transmission. Since a significant amount of state information mightotherwise require to be transmitted repeatedly over the air interface,this can result in significant improvements in efficiency of use of thebandwidth available over the radio interface. Nevertheless, if one ofsaid of one or more predetermined triggers is detected before expiry ofthe timing period measured by said timer, the current value associatedwith a given state information part may then be transmitted, to ensurethat the radio access node currently serving the user equipment hasaccess to the state information required for improved operation of theuser equipment.

In some embodiments, said one or more predetermined triggers comprisefailure of a connection between the user equipment and the radio accessnetwork.

In some embodiments said one or more predetermined triggers comprises amessage associated with handover between cells of the radio accessnetwork.

According to a fourth aspect of the invention, there is provided userequipment for use in a radio access network comprising cells that arecontrolled by radio access nodes, the user equipment comprising:

a data store for maintaining current state information relating to theuser equipment, the state information comprising at least one stateinformation part associated with one or more features for which stateinformation reporting may be configured in a cell, the at least onestate information part being associable with a plurality of differentvalues; and

a processor configured to:

initiate first reporting of a current value associated with at least agiven state information part to a radio access node;

activate a timer on the basis of the initiation of the first reporting;

determine whether to initiate second reporting of the current value to aradio access node on the basis of one or more predetermined triggers;and

initiate second reporting of the current value in response to detectionof one of said of one or more predetermined triggers before expiry of atiming period measured by said timer.

Further features and advantages of the invention will become apparentfrom the following description of preferred embodiments of theinvention, given by way of example only, which is made with reference tothe accompanying drawings.

Advantageous Effects of Invention

According to the present invention, some improvements in processinginformation relating to user equipment is provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block schematic representation of a communications systemaccording to some embodiments;

FIG. 2 shows a method of processing state information relating to userequipment according to some embodiments;

FIG. 3 shows a method of processing state information relating to userequipment according to some embodiments;

FIG. 4 shows a method of processing state information relating to userequipment according to some embodiments;

FIG. 5 shows a method of processing state information relating to userequipment according to some embodiments; and

FIG. 6 is a block schematic representation of a communications systemaccording to some embodiments.

MODE FOR THE INVENTION

FIG. 1 is a block schematic representation of a communications system100 according to some embodiments.

The communications system 100 includes a radio access network, generallyindicated in a dotted box in FIG. 1 and designated by reference 101. Insome embodiments, the radio access network 101 comprises an E-UTRAN. Atleast some embodiments are intended to be applicable to release 11(REL-11) and beyond of the E-UTRA. However, at least some embodimentsmay be applicable to other releases of the E-UTRA and/or other (radioaccess) systems.

The communications system 100 includes User Equipment (UE) 102. In someembodiments, the UE 102 is a mobile telephony device. However, othertypes of UE 102 are envisaged.

The radio access network 101 includes first and second radio accessnodes 103, 104. The first and second radio access nodes 103, 104 controlat least respective first and second cells 105, 106. It will beappreciated that one or both of the first and second radio access nodes103, 104 may control more than one cell. The first and second radioaccess nodes 103, 104 may be communicatively coupled by means of one ormore interfaces 107, 108, 109.

In some embodiments, the radio access nodes 103, 104 are evolved Node Bs(eNodeBs or eNBs). In such embodiments, the radio access nodes 103, 104may be able to interact directly with each other via an X2 interface 107and/or indirectly via respective Si interfaces 108, 109 to a CoreNetwork (CN) 110. In some embodiments, the first radio access node 103operates a first Radio Access Technology (RAT) and the second radioaccess node 104 operates a second, different RAT.

The UE 102 communicates with the first radio access node 103 via a firstradio link 111 and communicates with the second radio access node 104via a second radio link 112.

It will be appreciated that the communications system 100 may includemore than one UE 102 and the radio access network 101 may include morethan two radio access nodes and associated cells.

In some embodiments, one of the first and second radio access nodes, inthis case the first radio access node 103, is a source radio access node103 that is associated with a first cell 105. The source radio accessnode 103 may be configured to transmit state information relating to theUE 102. The other of the first and second radio access nodes, in thiscase the second radio access node 104, is a target radio access node 104that is associated with a second cell 106. The target radio access node104 is capable of receiving the state information from the source radioaccess node 103. The source radio access node 103 is configured totransmit the state information to the target radio access node 104 viathe at least one interface 107, 108, 109 between the source radio accessnode 103 and the target radio access node 104.

The UE 102 is configured to maintain current state information relatingto the UE 102. The state information comprises at least one stateinformation part that is associated with one or more features for whichstate information reporting may be configured in the first cell 105and/or the second cell 106. The at least one state information part isassociable with a plurality of different values. The state informationmay be at least partly dynamic.

In some embodiments, the state information comprises status informationrelating to the UE 102, for example relating to proximity to a ClosedSubscriber Group (CSG) cell, interest in MBMS services or in-deviceinterference. In some embodiments, the state information comprises UEcapability information, i.e. capability information relating to the UE102, which is dynamic and may change, for example support for RLFinformation availability and/or logged measurement informationavailability, UE category information, or power class (which may changefor example with the device is plugged into an external power source).One or more elements of the UE capability information may reflect thedata rate that the UE currently supports. The current state of thisinformation may depend on a task the UE 102 is performing e.g. playing agame, doing navigation, etc. In such cases the UE capabilities maychange, dependent on the current operational state of the UE 102.

Other types of state information that the UE 102 may report to the radioaccess network 101 are contemplated.

In some cases, the connection may change from the first cell 105 to thesecond cell 106. The connection may change, for example, as a result ofa handover or as a result of re-establishment following a connectionfailure. The UE 102 may detect such a connection change, for example byreceiving a handover command or by detecting the connection failure. Inembodiments in which the source radio access node 103 operates a firstRAT and the target radio access node 104 operates a second, differentRAT, this change in connection may be referred to as an inter-RAT cellchange.

In some embodiments, the source radio access node 103 receives stateinformation relating to the UE 102 and transmits the received stateinformation to the target radio access node 104.

In some embodiments, the source radio access node 103 is configured totransmit at least part of the state information in a message associatedwith the change in connection. Thus, in some embodiments, as part of thechange in connection (for example as part of handover preparation), thesource radio access node 103 provides the state information to thetarget radio access node 104. In some embodiments, the messageassociated with the change in connection comprises a handoverpreparation message. In some embodiments, the source radio access node103 is configured to include the at least part of the received stateinformation in an Access Stratum (AS)-context field in a handoverpreparation message. Thus, in some embodiments, the at least part of thestate information may be included in the AS-context field in aHandoverPreparationInformation message. In some embodiments, the sourceradio access node 103 is configured to include the at least part of thestate information in an information container, the information containerbeing a variable size string.

In some embodiments, the source radio access node 103 receives stateinformation reports from the UE 102. The state information reportsidentify changes to the state information relating to the UE 102. Insome embodiments, the UE 102 transmits state information reports only inthe event of a change to at least part of the state information.

Some embodiments comprise receiving at least some of the stateinformation from a radio access node (not shown in FIG. 1; see FIGS. 3to 5) to which the UE 102 was previously connected.

In some cases, the state information received from the previous radioaccess node is not comprehensible by the source radio access node 103,for example because the source radio access node 103 and the previousradio access node may support different specification releases and/orfunctionality. By implementing backwards compatibility in protocols, theradio access nodes may still be able to cooperate for the functionalitysupported by both radio access nodes. Whenever the protocols evolve,extension fields may be introduced for newly added functionality.Backwards compatibility may be provided by configuring radio accessnodes that do not support such newly added functionality and/or do notcomprehend the associated extension fields or parameters to ignore theextensions or parameters, as the case may be. Nodes that supporttransparent transfer or forwarding may be able to identify the end ofthe state information, for example based on the size of the container inwhich the state information is included, without having to comprehendthe details of the statue information (which is otherwise needed whenusing packed encoding rules (PER)).

In some cases, it may not seem beneficial or even desirable, tointroduce ‘transparent forwarding’ of state information from a previousradio access node to the source radio access node 103 when the stateinformation is not comprehensible by the source radio access node 103since such transparent forwarding would allow forwarding of stateinformation to nodes that do not comprehend the state information. Whileconnected to such nodes, the UE 102 cannot provide state informationreports and, hence, the forwarded state information might be outdatedwhen it reaches the next radio access node. In such cases, the transferof state information transparently may only serve to increase overallsignaling in the radio access network 101, which is generallyundesirable.

However, in some cases, transparent forwarding may be desirable. Forexample, it may typically be more difficult to upgrade femto radioaccess nodes than it is to upgrade macro radio access nodes.Consequently, it is quite possible that a femto radio access node wouldconform to an earlier (older) specification release than a macro radioaccess node. If the UE 102 operates on a frequency in which femto radioaccess nodes are deployed, the UE 102 may regularly connect to a radioaccess node that uses an old release that may not support stateinformation reporting. Since femto cells are relatively small, the stayby the UE 102 in such cells may be rather short. Thus, it is quitepossible that after passing through a femto cell, the UE 102 status isstill valid. In such cases, it may be desirable to provide support fortransparent forwarding of the state information by nodes that supporttransparent transfer but that may not support state informationreporting in relation to features for which state information reportingis added in later releases.

As explained above, is generally desirable that unnecessary stateinformation reporting by the UE 102 be minimized. As such, the UE 102 isconfigured to transmit a current value associated with a given stateinformation part to the target radio access node 104 in response todetecting at least one of one or more predetermined triggers thatindicate that the target radio access node 104 may not have received thecurrent value from the source radio access node 103. The UE 102 relieson the target radio access node 104 having received the current valuefrom the source radio access node 103 if said at least one of said oneor more predetermined triggers is not detected. Thus, in someembodiments, the at least one predetermined trigger acts as an indicatorthat the target radio access node 104 may not have received, is unlikelyto have received, or has not received, the current value from the sourceradio access node 103. In such cases, the UE 102 can report the currentvalue to the target radio access node 104 so that the target radioaccess node 104 has up-to-date state information relating to the UE.

In some embodiments, the one or more predetermined triggers includedetermining that the target radio access node 104 has not received thecurrent value from the source radio access node 103. In suchembodiments, the UE 102 reports the current value to the target radioaccess node 104 so that the target radio access node 104 has up-to-datestate information relating to the UE 102.

In some embodiments, the one or more predetermined triggers includedetermining that the current value has not been reported to the radioaccess network 101. In such embodiments, the UE 102 may determine thatthe target radio access node 104 has not received the current value,since the current value has not been reported. In response to detectingsuch a trigger, the UE 102 reports the current value to the target radioaccess node 104 so that the target radio access node 104 has up-to-datestate information relating to the UE 102

In some embodiments, the one or more predetermined triggers includedetermining that the current value may have been reported to the sourceradio access node 103 too late for the source radio access node 103 tohave transmitted it to the target radio access node 104. It is possiblethat the value associated with the given state information part and/orother state information relating to the UE 102 changes after the sourceradio access node 103 has provided the latest state information it hasrelating to the UE 102 to the target radio access node 104. Thissituation is generally referred to herein as a “late change”. In such asituation, the UE 102 may be configured to report the updated stateinformation immediately following a cell change. Thus, in someembodiments, in the event that the state information has changed afterthe source radio access node 103 provided the state information relatingto the target radio access node 104 (a late change), the UE 102 provides(again) the updated state information to the target radio access node104, possibly immediately, following a handover or other change inconnection.

However, the UE 102 may not know when exactly the source radio accessnode 103 provided the latest state information it had relating to the UE102 to the target radio access node 104. Accordingly, various mechanismsare provided by means of which the UE 102 can detect whether a latechange occurred. Two such mechanisms are discussed below: a timer-basedscheme and a scheme in which version information is exchanged betweenthe UE 102 and the radio access network 101. Other suitable mechanismsmay, however, be used.

For UEs 102 in connected mode, the radio access network 101 typicallyinitiates a cell change in response to a measurement report from the UE102 indicating that the current serving cell is not optimal from a radioperspective. It is, however, also possible for the radio access network101 to initiate a cell change for other reasons, for example the cellload. In such cases, handover may not be preceded by a measurementreport. This is often referred to as a ‘blind handover’. In such cases,the UE 102 cannot use the measurement report message as a roughindication of the time at which the source radio access node 103 islikely to have initiated handover preparation and have provided thelatest state information it had relating to the UE 102 to the targetradio access node 104. As such, the UE 102 may employ a timer to detectthe occurrence of a late change.

In some embodiments, the one or more predetermined triggers includedetermining that the current value was reported to the source radioaccess node 103 within at least one predetermined time period prior toreceiving a message relating to the change in connection. In someembodiments, the one or more predetermined triggers include determiningthat the current value was reported to the source radio access node 103within at least one predetermined time period prior to detecting afailure in a connection to the source radio access node. Thus, in someembodiments, in the event that the state information has changed withina certain time period before the UE 102 receives the handover command ordetects a failure with respect to the source radio access node 103, theUE 102 provides the updated state information to the target radio accessnode 104, possibly immediately, following handover or re-establishmentas the case may be.

In some embodiments, the at least one predetermined time period includesa time period specified in a telecommunications standard, for example inone or more releases of 3GPP specification number TS 36.300. In someembodiments, the at least one predetermined time period includes a timeperiod configured by the radio access network 101. Thus, in someembodiments, the time period during which a change in state informationwould trigger the UE 102 to provide an update may either by fixed (forexample a value specified in the standard) or may be configured by theradio access network 101.

In some embodiments, the at least one predetermined time period includesa time period associated with a handover message. In some embodiments,the at least one predetermined time period includes a time periodassociated with a connection re-establishment procedure. Thus, in someembodiments, for handover and re-establishment, different time periods,during which a change in state information would trigger the UE 102 toprovide an update, may be used.

In some embodiments, the one or more predetermined triggers includereceiving, from the target radio access node 104, a message comprisingat least one predetermined indicator from which it can be determinedwhether or not the target radio access node 104 has received the currentvalue from the source radio access node 103. In such embodiments, the UE102 can use the at least one predetermined indicator to determinewhether or not the target radio access node 104 has received the currentvalue from the source radio access node 103.

Another mechanism for the detection of late changes of UE stateinformation upon handover or other changes in connection is for the UE102 to provide a version identifier when reporting the stateinformation. Thus, in some embodiments, the at least one predeterminedindicator comprises a version identifier indicating a version of atleast the given state information part.

In some such embodiments, the one or more predetermined triggers includedetermining that the version identifier received from the target radioaccess node 104 does not correspond with a current version of the givenstate information part. Thus, in some embodiments, the UE 102 may usethe version identifier received in the message from the target radioaccess node 104 to determine whether the target radio access node 104has outdated state information relating to the UE 102. If the versionidentifier received in the message does not correspond to the currentversion of the state information, the UE 102 provides the updated stateinformation following the change in connection.

Some embodiments comprise including a version identifier indicating aversion of the given state information part when reporting the valueassociated with the given state information part to the radio accessnetwork 101. Some embodiments comprise including a version identifierindicating a version of the given state information part when reportinga change in the value associated with the given state information partto the radio access network 101. Some such embodiments compriseadvancing the version identifier indicating the version of the givenstate information part upon transmitting the change in the valueassociated with the given state information part to the radio accessnetwork 101. Some such embodiments comprise advancing the versionidentifier indicating the version of the given state information partupon reporting the change in the value associated with the given stateinformation part to the radio access network 101.

Thus, in some embodiments, whenever the UE 102 provides stateinformation, it includes a version identifier. In some cases, the UE 102steps the version identifier whenever it transfers state informationthat is different from state information that was previously transmittedto the radio access network 101. The UE 102 may consider the stateinformation to have been transferred successfully if one or moreappropriate acknowledgements is received at lower layers. In certaincases, the UE 102 steps the version identifier whenever it transmitsstate information that is different from state information that waspreviously transmitted, regardless of whether the transmitted stateinformation was known to be received successfully by the radio accessnetwork 101, since an acknowledgement might not be received even thoughthe radio access network 101 had successfully received the stateinformation.

For state information parts whose associated values changes frequently,late changes are not unlikely. A separate version identifier may beapplied to such state information parts. In other cases in which latechanges are unlikely, it may be sufficient to use one, common versionidentifier to cover some or all state information parts collectively.Thus, in some embodiments, the version identifier is a common versionidentifier that indicates a version of both the given state informationpart and at least one additional state information part. Thus, in someembodiments, a single version identifier (referred to herein as a“common version identifier”) may be used to cover a plurality ofseparate state information parts.

Some such embodiments comprise including the common version identifierwhen reporting the value associated with the given state informationpart and/or the at least one additional state information part to theradio access network 101. Some such embodiments comprise including thecommon version identifier when reporting a change in the valueassociated with the given state information part and/or the at least oneadditional state information part to the radio access network 101. Somesuch embodiments comprise advancing the common version identifier upontransmitting the change in the value associated with the given stateinformation part and/or the at least one additional state informationpart to the radio access network 101. Thus, in some embodiments, whenusing a common version identifier, the UE 102 steps the versionidentifier whenever it transfers a state information part that has avalue that is different from the value associated with the stateinformation part that was previously transmitted.

In some such embodiments, the one or more predetermined triggersinclude: determining that the common version identifier received fromthe target radio access node 104 does not correspond with a currentcommon version of the given state information part and the at least oneadditional state information part; and determining that the valuecurrently associated with the given state information part is differentfrom the value associated with a version of the given state informationpart as indicated by the received common version identifier. Thus, insome embodiments, in the event that the common version identifierreceived in the message from the target radio access node 104 does notcorrespond with the version of the state information that the UE 102has, the UE 102 provides updated state information including at leastthe values of the state information parts that changed compared to thosein relation to the version identifier received in the message from thetarget radio access node 104.

In some embodiments, the message received from the target radio accessnode 104 relates to handover. In other embodiments, the message receivedfrom the target radio access node 104 relates to a connectionre-establishment procedure. In some embodiments, the message receivedfrom the target radio access node relates to neither a handover commandnor a connection re-establishment procedure. For example, the messagemay be a dedicated message from the target radio access node or mayrelate to one or more procedures other than handover orre-establishment.

In some embodiments described above, a version identifier is used todetermine whether the last (successful) state information report inwhich the value associated with the given status element was reportedwas potentially too late for the source radio access node 103 to havetransmitted it to the target radio access node 104. However, the networkneed not provide an indication that it received a previous valueassociated with the given state information part from another radioaccess node, such as the source radio access node 103. This as this canbe indicated implicitly, for example by the absence of the versionidentifier or by the inclusion of a specific version identifier value.For example upon change a from a cell in which the UE 102 is notconfigured to report on the given state information part to a cell inwhich the UE 102 is configured to report on the given state informationpart, the UE 102 may (again) provide the updated value associated withthe given state information part in the event that the target radioaccess node 104 indicates in a message that it transmits to the UE 102that it does not have the updated value associated with the given stateinformation part by not providing any version identifier, by means of aspecial or predefined version identifier value or by means of a separateindication, for example by using a separate indication for each stateinformation part in the event that a common version identifier is used.

Thus, in some embodiments, the given state information part isassociable with a version identifier that indicates a version of thegiven state information part and the at least one predeterminedindicator includes a predetermined version identifier. In someembodiments, the given state information part is associable with aversion identifier that indicates a version of the given stateinformation part and the at least one predetermined indicator includesthe absence of a version identifier associated with the given stateinformation part.

In some embodiments, the one or more predetermined triggers includedetermining that the source radio access node 103, and/or or one moreradio access nodes to which the UE 102 was previously connected sincethe value currently associated with the given state information part wasreported to the radio access network 101, does not support forwarding ofstate information relating to the UE 102.

The indication that the target radio access node 104 does not havecurrent state information may be provided in at least two differentways. One way in which the target radio access node 104 may indicatethat it does not have the current state information is by indicatingthat it does not have any value associated with a particular stateinformation part, for example using dedicated signaling. Another way inwhich it may be indicated that the target radio access node 104 does nothave the current state information is for the radio access network 101to indicate whether each cell or associated radio access node supportstransparent transfer of state information relating to the user, forexample by using broadcast signaling. In the latter case, the UE 102assumes that target radio access node 104 does not have a current valueassociated with the given state information part if the UE 102 wasconnected to one or more cells that did not support transparent transferof state information since it last provided an updated value associatedwith the given state information part to the radio access network 101.

Thus, the target radio access node 104 may indicate whether or not ithas a value associated with the given state information part. The radioaccess network 101 may, also or alternatively, indicate for each cellwhether or not the cell supports transparent transfer of stateinformation relating to the UE 102. This may either be provided by usingbroadcast signaling, such as system information, or by using dedicatedsignaling as explained above. In the event of using dedicated signaling,the UE 102 assumes that the target radio access node 104 does not have avalue associated with the given state information part if the UE 102 wasconnected to one or more cells that did not support transparent transferof status info since it last provided a state information report for theone or more features associated with the given state information part.

Some embodiments comprise transmitting the value currently associatedwith the given state information part to the target radio access node104 in response to said detecting at least one predetermined triggeronly if the given state information part is associated with one or morefeatures for which state information reporting is configured in thesecond cell 106.

One consideration is what state information the UE 102 should includewhen repeating the state information reporting due to a late change.Different radio access nodes may configure state information reportingfor different features, for example because the radio access nodes areprovided by different vendors and do not support the same set offeatures. For example, in the first cell 105, the UE 102 may beconfigured to perform state information reporting for features A and B,while in the second cell 106 the UE 102 may be configured to performstate information reporting for features B and C. In embodimentsdescribed above, unnecessary repeating of state information reportingmay be reduced for the features that are shared between the first cell105 and the second cell 106, in this case feature B. Additionally, theUE 102 may provide a state information report for the features that arenewly configured by the second cell 106; those that are not shared withfirst cell 105? in this case feature C. Furthermore, the UE 102 need notrepeat state information reporting due to a late change in relation to afeature, such as feature A in the example above, that is not configuredin the second cell 106. Thus, in some embodiments, the UE 102 may beconfigured to repeat updated state information following a handover oranother change in connection only if the late change concerned one ormore features that are configured in the second cell 106 (irrespectiveof whether or not they are also configured in the first cell 105).

In some embodiments, the one or more predetermined triggers includedetermining that the given state information part is associated with oneor more features for which state information reporting is configured inthe second cell 106 and for which state information reporting is notconfigured in the first cell 105. As such, whenever the UE 102 movesfrom a cell associated with a radio access node that does support stateinformation reporting for a particular feature to a node supportingreporting of the particular feature, the UE 102 reports the currentvalue associated with the given state information part. Thus, in someembodiments, following a change in connected mode from a first cell 105in which the UE 102 is not configured to report (changes to) aparticular state information part to a second cell 106 in which the UE102 is configured to report (changes to) the particular stateinformation part, the UE 102 initiates a state information reportregardless of whether or not the value associated with the particularstate information part has changed compared to what was included in apreviously sent state information report identifying a previous valueassociated with the particular state information part.

In some embodiments, the given state information part is associated withone or more features for which state information reporting is configuredin the second cell 106 and for which state information reporting is notconfigured in the first cell 105.

In other embodiments, the given state information part is associatedwith one or more features for which state information reporting isconfigured in both the first cell 105 and the second cell 106. Suchembodiments reduce unnecessary state information reporting by the UE 102following a cell change, for example handover or re-establishment, inconnected mode between cells in which the UE 102 is configured to reportchanges or updated associated with the given state information in bothcells.

State information reporting by the UE 102 may include several proceduralaspects, at least some of which may be handled in a common manner, whileother aspects may need to be handled separately in relation to some ofthe state information parts.

Some embodiments comprise transmitting an additional current valueassociated with a further given state information part to the targetradio access node in response to detecting at least one of one or morepredetermined triggers that indicate that the target radio access nodemay not have received the additional current value from the source radioaccess node and relying on the target radio access node having receivedthe additional current value from the source radio access node if saidat least one of said one or more predetermined triggers is not detected.In some embodiments, at least the current value and the additionalcurrent value are included in a single message to the target radioaccess node. Thus, in some cases, a common message or procedure isintroduced for the common reporting of several different stateinformation parts. Common procedural aspects are specified at the levelof this common message. Nevertheless, it may still be desirable to havea procedural specification for the state information parts included inthe common message. This may be achieved by treating the different stateinformation parts as if they were separate messages, so that the commonmessage would be considered as a list of individual messages.

FIG. 2 shows a method of processing state information relating to userequipment according to some embodiments.

At least some embodiments described above may result in modifications toprocedures and information specified in 3GPP TS 36.331, “EvolvedUniversal Terrestrial Radio Access (E-UTRA); Radio Resource Control(RRC); Protocol specification”. Some modifications may include:

-   -   using a common message (UEStateIndication) to report at least        the current value associated with the given state information        part, for example following detection of late changes during        handover;    -   extending the AS-Context field within the HandoverPreparation        message to include at least the current value, possibly as well        as a version identifier; and    -   extending the RRCConnectionReconfiguration message, which is        used to convey a handover command, to include the version        identifier.

In some embodiments, the other config field, within anRRCConnectionReconfiguration message may be used to indicate timinginformation. In some embodiments, a UEStateInformation message may serveas a common state information message that includes an indication of(one or more) current version(s) of the state information. TheUEStateInformation message my include both one of more state informationvalues, for example indicating MBMS interest, as well as one or moreversion identifiers. In some embodiments, a new field may be providedwithin the RRCConnectionReconfiguration message to indicate theversion(s) of state information that is available in the E-UTRAN uponhandover. In some embodiments, the MeasurementReport message that the UEsends to the E-UTRAN may also be modified.

FIG. 3 shows a method of processing state information relating to userequipment in a communications system according to some embodiments. Inthese embodiments, a single, common version identifier is used to coverall of the state information parts making up the state information.

In this example, the state information relating to the user equipmentcomprises three different state information parts, denoted A, B and Cand associated with features A, B and C respectively.

Three cells are depicted in which state information reporting isconfigured for different features. State information reporting forfeatures A and B is configured in a first cell. State informationreporting is not configured at all in a second cell. However, the secondcell supports transparent forwarding of state information; in otherwords, although the second radio access node that controls the secondcell does not comprehend state information that it receives from thefirst radio access node that controls the first cell, it forwards thestate information to the third radio access node that controls the thirdcell. State information reporting for features B and C is configured ina third cell.

The UE 102 establishes an initial connection to the first radio accessnode, where it performs state information reporting for features A and Band includes a version identifier Vn=1 when reporting. At time T1, whilethe UE 102 is still in the first cell, the value of the stateinformation part associated with feature A changes. The UE 102 transmitsthe updated value of the state information part associated with featureA to the first radio access node and steps the version identifier toVn=2.

The UE 102 then moves, in connected mode, to the second cell. The firstradio access node transmits the latest state information it has relatingto the UE 102 to the second radio access node even though the secondradio access node does not comprehend the state information.

At time T2, while the UE 102 is in the second cell, the value of thestate information part associated with feature B changes. Since thereporting of changes associated with feature B is not configured in thesecond cell, the UE 102 does not report the changed value to the secondradio access node and does not step the version identifier associatedwith the state information.

The UE 102 then moves, in connected mode, from the second cell to thethird cell. The second radio access node transmits the latest stateinformation it has relating to the UE 102? which is the stateinformation it received from the first radio access node? to the thirdradio access node. In this case, the second radio access nodetransparently transfers the state information to the third radio accessnode.

The UE receives a message from the third radio access node whichincludes the version identifier Vn=2. This corresponds to the version ofthe state information that was transparently forwarded by the secondradio access node.

The UE 102 determines that the third cell supports reporting of featuresB and C. The UE 102 does not transmit the current value associated withfeature A (which was changed at time T1) to the third radio access nodesince reporting of feature A is not configured in the third cell. The UE102 determines that it has not transmitted the updated value associatedwith feature B (which was changed at time T2) to the radio accessnetwork. The UE 102 also determines that it has not transmitted the(current) value associated with feature C to the radio access network,since reporting of feature C was not configured in either the first orsecond cell. As such the UE 102 transmits, in a common message, thecurrent value associated with feature B (which was updated at time T2)and the current value associated with feature C at time T3 while the UE102 is connected to the third cell and updates the version identifierassociated with the state information to Vn=3.

FIG. 4 shows a method of processing state information relating to UE 102in a communications system according to some embodiments. In theseembodiments, a single, common version identifier is used to cover all ofthe state information parts making up the state information.

The method shown in FIG. 4 is similar to that shown in FIG. 3. However,in this example, reporting of feature A, in addition to features B andC, is configured in the third cell.

In particular, the UE 102 establishes an initial connection to the firstradio access node, where it performs state information reporting forfeatures A and B and includes a version identifier Vn=1 when reporting.At time T1, while the UE 102 is still in the first cell, the value ofthe state information part associated with feature A changes. The UE 102transmits the updated value of the state information part associatedwith feature A to the first radio access node and steps the versionidentifier to Vn=2. However, in this example, the UE 102 reports thechanges value associated with feature A just prior to the UE 102 moving,in connected mode, to the second cell.

The first radio access node transmits the latest state information ithas relating to the UE 102 to the second radio access node even thoughthe second radio access node does not comprehend the state information.In this example, the first radio access node did not receive the updatedstate information from the UE 102 in time for it to be transmitted tothe second radio access node. As such, the state information transmittedby the first radio access node to the second radio access node is theinitially reported state information associated with the versionidentifier Vn=1.

At time T2, while the UE 102 is in the second cell, the value of thestate information part associated with feature B changes. Since thereporting of changes associated with feature B is not configured in thesecond cell, the UE 102 does not report the changed value to the secondradio access node and does not step the version identifier associatedwith the state information.

The UE 102 then moves, in connected mode, from the second cell to thethird cell. The second radio access node transmits the latest stateinformation it has relating to the UE 102? which is the stateinformation it received from the first radio access node? to the thirdradio access node. In this case, the second radio access nodetransparently transfers the state information to the third radio accessnode. In this example, the transparently transferred state informationinclude the version identifier Vn=1.

The UE 102 receives a message from the third radio access node whichincludes the version identifier Vn=1. This corresponds to the version ofthe state information that was transparently forwarded by the secondradio access node.

The UE 102 determines that the third cell supports reporting of featuresA, B and C. The UE 102 determines that the third radio access node doesnot have the current value associated with feature A since the versionidentifier it received from the third radio access node (Vn=1) does notcorrespond with the current version of the state information (Vn=2). TheUE 102 determines that the value associated with feature A changedbetween the first and second version and determines that the currentvalue associated with feature A is to be transmitted to the third radioaccess node. The UE 102 determines that it has not transmitted theupdated value associated with feature B (which was changed at time T2)to the radio access network. The UE 102 also determines that it has nottransmitted the (current) value associated with feature C to the radioaccess network, since reporting of feature C was not configured ineither the first or second cell. As such the UE 102 transmits, in acommon message, the current value associated with feature A (which wasupdated at time T1), feature B (which was updated at time T2) and thecurrent value associated with feature C at time T3 while the UE 102 isconnected to the third cell and updates the version identifierassociated with the state information to Vn=3.

FIG. 5 shows a method of processing state information relating to userequipment in a communications system according to some embodiments. Inthese embodiments, a single, common version identifier is used to coverall of the state information parts making up the state information.

In this example, the state information relating to the user equipmentcomprises three different state information parts, denoted A, B and Cand associated with features A, B and C respectively.

Four cells are depicted in which state information reporting isconfigured for different features. State information reporting forfeatures A and B is configured in a first cell. State informationreporting is not configured at all in a second cell. In this example,the second cell does not support transparent forwarding of stateinformation. State information reporting for features B and C isconfigured in a third cell. State information reporting for features Aand B is configured in a fourth cell.

The UE 102 establishes an initial connection to a first radio accessnode that controls the first cell, where it performs state informationreporting for features A and B and includes a version identifier Vn=1when reporting. At time T1, while the UE 102 is still in the first cell,the value of the state information part associated with feature Achanges. The UE 102 transmits the updated value of the state informationpart associated with feature A to the first radio access node and stepsthe version identifier to Vn=2.

The UE 102 then moves to the second cell. However, since the secondradio access node that controls the second cell does not supporttransparent forwarding of state information, the second radio accessnode does not receive state information from the first radio accessnode.

At time T2, while the UE 102 is in the second cell, the value of thestate information part associated with feature B changes. Since thereporting of changes associated with feature B is not configured in thesecond cell, the UE 102 does not report the changed value to the secondradio access node and does not step the version identifier associatedwith the state information.

The UE 102 then moves the second cell to the third cell. Since thesecond radio access node does not support transparent forwarding ofstate information, the third radio access node does not receive thestate information from the second radio access node.

The UE 102 receives a message from the third radio access node whichincludes a predetermined indicator from which the UE 102 can determinethat the third radio access node does not have current stateinformation. For example, the third radio access node may include noversion identifier or a special parameter in a message to the UE 102.

The UE 102 determines that the third cell supports reporting of featuresB and C. The UE 102 does not transmit the current value associated withfeature A (which was changed at time T1) to the third radio access nodesince reporting of feature A is not configured in the third cell. The UE102 determines that it has not transmitted the updated value associatedwith feature B (which was changed at time T2) to the radio accessnetwork. The UE 102 also determines that it has not transmitted the(current) value associated with feature C to the radio access network.As such the UE 102 transmits, in a common message, the current valueassociated with feature B (which was updated at time T2) and the currentvalue associated with feature C at time T3 while the UE 102 is connectedto the third cell and updates the version identifier associated with thestate information to Vn=3.

At time T3, while the UE 102 is in the third cell, the value of thestate information part associated with feature B changes. Since thereporting of changes associated with feature B is configured in thethird cell, the UE 102 reports the changed value to the third radioaccess node and step the version identifier associated with the stateinformation to Vn=4.

The UE 102 then moves, in connected mode, from the third cell to thefourth cell. The third radio access node transmits the latest stateinformation it has relating to the UE 102 to the fourth radio accessnode and includes the version identifier Vn=4.

The UE receives a message from the fourth radio access node whichincludes the version identifier Vn=4.

The UE 102 determines that the fourth cell supports reporting offeatures A and B. However, the UE 102 remembers determining that thesecond cell did not support transparent transfer of state informationand that the fourth radio access node will not have the current valueassociated with feature A since reporting of feature A was notconfigured in the third cell. As such, the UE 102 determines that itwill need to transmit the current value associated with feature A to thefourth radio access node. The UE 104 compares the version identifier itreceived from the fourth radio access node, Vn=4, to the current versionidentifier, Vn=4, and determines that the fourth radio access node hasthe current value associated with feature B. As such, the UE 104determines that it need not transmit the current value associated withfeature B to the fourth radio access node. Accordingly, the UE 102transmits the current value associated with feature A to the fourthradio access node and updates the version identifier associated with thestate information to Vn=5.

In some embodiments described above, the target radio access node 104controlling the second cell 106 does not have up to date stateinformation as a result of a change in connection from the source radioaccess node 103 to the target radio access node 104. However, at leastsome of the procedures described above, in particular relating todetermining when the UE 102 should provide a new state informationreport, may also apply when the UE 102 moves from one cell to anothercell, even if both cells are controlled by the same radio access node.In such cases, the UE may be configured to determine whether there is aneed to provide a new state information report.

FIG. 6 is a block schematic representation of a communications system600 according to some embodiments. The communications system 600depicted in FIG. 6 includes some elements that are the same as, or aresimilar to, elements shown in FIG. 1. Such elements are given the samereference numerals as used above in relation to FIG. 1 but areincremented by five hundred.

The communication system 600 depicted in FIG. 6 includes a radio accessnetwork 601, which includes a radio access node 604. The radio accessnode 604 controls first and second cells 605, 606. UE 602 cancommunicate with the radio access node 604 via a radio interface 611.

Some embodiments provide a method of processing state informationrelating to user equipment in a communications system 600 comprising aradio access network 601. The communications system 600 comprises afirst cell 605 and a second cell 606. In some embodiments, the firstcell 605 and the second cell 606 are controlled by the same radio accessnode 604. The method comprises maintaining current state informationrelating to the user equipment 602. The state information comprises atleast one state information part associated with one or more featuresfor which state information reporting may be configured in the firstcell 605 and/or the second cell 606. The at least one state informationpart is associable with a plurality of different values. The UE 602 isconfigured to detect a connection change to the second cell. The UE isconfigured to transmit a current value associated with a given stateinformation part to a radio access node 604 associated with the secondcell 606 in response to detecting at least one of one or morepredetermined triggers that indicate that the radio access node 604associated with the second cell 606 may not have the current value. TheUE 602 is configured to rely on the radio access node 604 associatedwith the second cell 606 having the current value if said at least oneof said one or more predetermined triggers is not detected.

Some embodiments provide a method of processing state informationrelating to user equipment in a communications system 600 comprising aradio access network 601. The communications system 600 comprises atleast one cell 605, 606 that is controlled by the radio access node 604.The method comprises maintaining current state information relating tothe user equipment 602. The state information comprises at least onestate information part associated with one or more features for whichstate information reporting may be configured in the at least one cell605, 606. The at least one state information part is associable with aplurality of different values. The UE 602 is configured to detect aconnection change in relation to the at least one cell 605, 606. The UEis configured to transmit a current value associated with a given stateinformation part to a radio access node 604 associated with the at leastone cell 605, 606 in response to detecting at least one of one or morepredetermined triggers that indicate that the radio access node 604associated with the at least one cell 605, 606 may not have the currentvalue. The UE 602 is configured to rely on the radio access node 604associated with the second cell 606 having the current value if said atleast one of said one or more predetermined triggers is not detected. Insuch embodiments, the UE 602 may perform such processing even wherethere is no change of cell, for example in the case of re-establishing aconnection to the radio access node 604 following detecting of a failuretherewith.

At least some embodiments described above reduce the need for the UE102, 602 to repeat state information reporting after every cell changein connected mode, for example as part of a handover or connectionre-establishment procedure. In some embodiments, a source RAN node, suchas a source eNb, forwards UE state information to a target RAN node,such as a target eNb. In some embodiments, following a cell change inconnected mode from a cell in which the reporting of UE stateinformation is not configured to a cell in which the reporting of UEstate information is configured, the UE 102, 106 always provides updatedstate information. In some embodiments, following a cell change inconnected mode between cells in which the reporting of UE stateinformation is configured, the UE 102 provides updated state informationif: at least part of the state information changed shortly before thecell change and/or if a ‘version’ received from the target radio accessnode 104 indicates that the target radio access node 104 does not haveup-to-date UE state information. In some such embodiments, a version canbe exchanged on the basis of individual state information parts or acommon version can be used to cover a plurality of state informationparts. In some embodiments, a common message or procedure may be used tospecify the elements (information as well as procedural aspects) thatare common for all state information parts only once. At least someembodiments provide mechanisms to limit repeated state informationreporting by the UE 102, 602 after every cell change in connected mode.Some embodiments seek to minimize the repetition, by transferring stateinformation from a source node to a target node, complemented with theUE 102, 062 providing one or more state information reports in the eventthat the state information may have changed after the source nodetransferred the state information to the target node.

The above embodiments are to be understood as illustrative examples ofthe invention. Further embodiments of the invention are envisaged.

In the above embodiments, the version identifier may be a versionnumber. Other types of version identifier such as letters or othersymbols or parameters are envisaged. Furthermore, although embodimentsabove refer to a ‘value’ associated with a state information part, itwill be appreciated that the value need not be numeric and may dependupon possible states of one or more features with which the stateinformation part may be configured.

It is to be understood that any feature described in relation to any oneembodiment may be used alone, or in combination with other featuresdescribed, and may also be used in combination with one or more featuresof any other of the embodiments, or any combination of any other of theembodiments. Furthermore, equivalents and modifications not describedabove may also be employed without departing from the scope of theinvention, which is defined in the accompanying claims.

What is claimed is:
 1. A method by a terminal in a wirelesscommunication system, the method comprising: transmitting, to a sourceradio access node, a first message including state information of aterminal; receiving, from the source radio access node, a radio resourcecontrol (RRC) message including information for performing a handoverfrom the source radio access node to a target radio access node;establishing a connection to the target radio access node based on theinformation included in the RRC message; and transmitting a secondmessage including the state information of the terminal to the targetradio access node, when the first message was transmitted during apredetermined time period prior to the receiving of the RRC message.